It has been known for some time that certain cereals, notably wheat, can be caused to expand or "puff" by subjecting them to a heating and pressure varying treatment. This treatment causes the cereals to exhibit physical characteristics substantially resembling those of an expanded material, but does not detrimentally affect their food value. Indeed, by making the cereal more palatable the food value can be considered as being increased by such treatment.
Known machines for performing this treatment, essentially perform successive cooking pressurisation and expansion operations on the cereal. Conventional machines, however, even if provided with control apparatus for performing these operations in an almost automatic manner, nevertheless suffer from a number of operating disadvantages which reduce their efficiency. More particularly, in current machines for the production of puffed cereals, especially those provided with a pair of rotatable pressurisable heatable drums as the essential components of the machines, the means for filling the drums at the beginning of each treatment cycle do not operate in an entirely automatic manner.
Likewise, each drum is provided with a sealing door to enable the drum to be pressurised, and the closure of the sealing door of each individual drum, after having been filled has to be effected manually in conventional machines, with a consequent unwanted interruption of the operating cycle. This arises largely from the fact that the drum has to be rotated about a substantially horizontal axis to perform the puffing treatments whereas the sealing door is most conveniently located at one end of the drum, which is not the most convenient orientation for filling.